Optical investigations of dynamic vacuum arc mode changes with different axial magnetic field contacts

By using a high-speed charge-coupled device (CCD) video technique, three different axial magnetic field contact systems (i.e., unipolar, bipolar, and quadrupolar systems) are investigated at an arc current of 10 kA. Video recordings were compared to computer simulations of light emission emitted at the side-on of diffuse and diffuse columnar arcs. The computer images reproduced typical trends, such as stronger light intensities in front of the cathode caused by higher-plasma densities in this region. A low-current dc vacuum arc was initiated by contact separation before the high current was injected at a fixed contact distance of 10 mm. Videos were taken from two directions perpendicular to each other to localize the vacuum arc properly. From these investigations, the transient development of vacuum arc under different axial magnetic field profiles can be visualized. The results were interpreted with respect to the behavior of the vacuum arc in the second half cycle after an eventual reignition.